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Beginners / Re: LC filtering for combined Vref/VDD of ADC
« Last post by pcprogrammer on Today at 06:30:49 am »Better way of doing this kind of thing is to create separate supplies for both analog and digital. Can be done with ferrite beads, resistors and capacitors coming of of the same supply voltage. By matching the supply voltage of both the digital and analog parts by trimming the series resistors there is little risk in exceeding maximum input voltages. The ADC works down to 2.7V and most likely the MCU you are using will also allow for some deviation of the supply voltage.
Also using multiple different value capacitors in the decoupling helps in reducing the noise. A friend of mine who is much more of an expert advised me to use parallel 100nF, 10nF and 1nF capacitors before and after the ferrite bead, and then the series resistor followed by a larger capacitor like 10uF. Then still add the 100nF decoupling capacitor advised for most IC's. See page 18 of the MCP3202 datasheet.
The different value capacitors seem to have different responses at different frequencies and therefore do a better job in filtering a wider spectrum, so I'm told.
Also using multiple different value capacitors in the decoupling helps in reducing the noise. A friend of mine who is much more of an expert advised me to use parallel 100nF, 10nF and 1nF capacitors before and after the ferrite bead, and then the series resistor followed by a larger capacitor like 10uF. Then still add the 100nF decoupling capacitor advised for most IC's. See page 18 of the MCP3202 datasheet.
The different value capacitors seem to have different responses at different frequencies and therefore do a better job in filtering a wider spectrum, so I'm told.